GRASS map display windows are no ``normal'' windows. Rather, they display geographical data with coordinates. These windows are called "monitors" in GRASS and are managed with the d.mon command or through the Display->Monitors menu in TclTkGRASS.
You can open several different monitors at once. Use d.mon start= to start the monitor of your choice and d.mon select= to select the monitor you want to display data on next. To stop a monitor, use d.mon stop= or simply click on the closing button provided by your window manager. You can also resize a monitor the way you would resize any window in your window manager.
GRASS offers the possibility to divide a monitor into several distinct frames. This gives you the opportunity to create a more sophisticated layout of your maps and other data. For example, you can create a frame for header information (title, date, etc), a frame for the actual map, a frame for footer information (author, sources, etc), a frame for the legend, etc, etc. The module for frame creation is d.frame and it is quite simple to use (see the manual page for details):
d.frame -c frame=title at=90,100,0,100 # create a title frame echo "TITRE" | d.text -b size=75 at=45,30 # write the title into the title frame d.frame -c frame=map at=10,90,0,100 # create a map frame d.rast combel # draw a raster map into that frame d.vect autoroute col=violet # draw a vector map into the same frame d.frame -c frame=legend at=0,10,0,100 # create a legend frame echo "Cartography: M. Lennert" | d.text size=20 at=75,50 # draw text in the legend frame d.barscale at=10,920 # create a barscale in the legend frame